Ultra-small protein single-chain nanoparticles (SCNPs) offer promising potential for biomedical applications. Building on advances in synthetic polymer chain collapse through intramolecular cross-linking, this proposal aims to apply these principles to proteins using bioengineered Consensus TetratricoPeptide Repeat (CTPR) proteins as model systems. CTPR5-WT and CTPR5-K4, which differ in Lysine content, are identified as target proteins for structural analysis using SAXS. By systematically altering the functional sites along the polypeptide chain, this research seeks to reveal key design principles for developing advanced protein-based nanoparticles.